1. Field of the Invention
The present invention relates to technology for licensing the utilization of digital contents in a computer, particularly relates to the issue of a license which certificates that the user is licensed to use digital contents and the verification of the legitimacy of the license.
2. Description of the Related Art
As the Internet is rapidly popularized, business that sells digital contents including digital data such as an image, sound, a projected image and software via the Internet is being popular. From the viewpoint of a provider of digital contents, the use of the Internet has a merit that the cost for the packaging of digital contents and distribution can be saved, and from the viewpoint of a consumer, the use of the Internet has a merit that a consumer can get digital contents at home. Undoubtedly, the provision of digital contents via the Internet is to become the mainstream of business based upon digital contents in future.
It is the most serious problem in currently selling digital contents that the charging a right fee from the user of digital contents is difficult. Recently, electronic payment is starting to be ready to operate and the transfer of money itself is becoming safe. Therefore, as long as a user of digital contents has a will to pay, a problem is hardly caused. However, it is very easy for a person unwilling to pay to copy and use contents because of the characteristic of digital contents that copying is possible without any trace.
A method currently most often adopted in relation to the problem described above is access control in a web site.
According to the method, a consumer downloads digital contents from a web site in the Internet. At the site, access from a consumer is controlled and only a consumer who paid a fee can download digital contents. This method can charge a consumer who accesses the site a fee, however, it is a problem that digital contents after they are downloaded can be copied and their fee cannot be got from the user of the copy. However, this method can charge at least a consumer who downloads digital contents a fee and the system for this method is simple and easy to install, therefore, many providers utilize the method.
A technique devised to also charge a user of copied digital contents a fee is a method using data called a software key. It is a method used for selling software and is often used for selling shareware.
According to the method, a provider of digital contents determines a set of digital data called a software key effective for digital contents provided by the provider and a method of verifying the effectiveness of the software key. A method of verifying a software key is involved in digital contents and only when an effective software key is input; the use of the digital contents is permitted. As a software key is sent to only a consumer who paid the fee of digital content, it is only the consumer who paid the fee of digital contents that can use the digital contents. Conversely, a consumer who wants to use digital contents is necessarily required to buy a software key from a provider of the digital contents.
In a system that a provider of digital contents determines a set of an effective software key and a method of verifying the effectiveness of the software key, a provider of digital contents has to bear the development cost related to the software key and the management cost of selling and issuing the software key. A software key is digital data also called a certificate for certifying the right of a consumer to use digital contents and resistance to various problems related to security such as leakage, forgery and copying of a software key is required. The development and management of such a system increase a cost, become a serious obstacle when a provider of digital contents starts selling digital contents and give disadvantage of a rise in a price to a consumer.